Separator



Fb. 16, 1937. c. R. HOLDEN Er AL y 2,071,261

SEPARATOR 4 Filed Aug. 14, .1935 3 Sheets-Sheet 2 lllllMllmlHL Patented Feb. 16, 19.37

UNITED STATES l PAT-ENT OFFICE sEPARATon CharlesY Revell Holden and 'Miguel Droliinsky, Chicago, Ill.; said Drobinsky assigner to said Holden Application August 14, 1935, serial No, 3649s Previously, there-have been many attempts to increase the effectiveness of mercury amalgamation process by the 'use of Aa direct current passed through the metalliferous suspension,v the mercury amalgamatedsurface being the cathode or negative ,pulp of the circuit. It has long been known that the chief diiiiculty in amalgamation processes of this typehas been to keep the mercury pure, to prevent the mercury from flouring or dividing up into small globules, and to keep the mercury interface with the pulp clean. It is common knowledge in theart that by the passage of 'a direct electric current, either with or without sodium or some other chemicals, the surface of the mercury for amalgamation is imf proved.

While a direct current passed through the mercury promotes amalgamation by releasing nascent hydrogen, which'cleanses the mercurypulp interface, the entry, exit,'and-passage of the current -through the mercury actually creates oxidation and fiouring of the mercury. The fa 'vorable cleansing action of the released nascent hydrogen and the favorable lessening of the interfaced surface tension by the agitation of the interface, are often more than offset by the loss of mercury available for amalgamation.

The' electrode which serves to conduct the direct current into the mercury, unless it is of a material which will not react with mercury, forms undesirable mercury alloys and combinations.

''he passage of the current from the negative electrode into the mercury causesdthe formation of dark mercury oxides, which mercury oxides generally collect on thesurfaceof the mercury and work their way towardthe positive electrode. Such effects render a portion of the mercury surface unavailable forj amalgamation purposes. v

After a run of severakhours, moreover, it will be vfound that a substantial percentage of the mercury has been rendered inactive' for amalgamation purposes through theformation of the mercury alloys and mercury oxides. These conditions have rendered such devices either inoperable or very ineilicient for long-runs.

It has been discovered that by insulating the mercurycarrying plate or holder fronithetrough or groove carrying the, pulp, and by passing the electrical current into the pulp by terminals end-l ing therein'and not coming into contact with the mercury itself or with 'the amalgamation plate,

the currentwill pass along the interface with the favorable results desired, and without the deleterious effects discussed -inthe previous paragraph. While a. portion of the current passes directly through the pulp, a portion enters the mercury interface and ows along it, creating the desired nascent hydrogen and modifying the surface tensions at the interface so as to sharply increase therspeed and extent of amalgamation. Apparently a portion of the `hydrogen enters the surface of the mercury, creatinga spongy condition at the interface which modies the surface tension, clea the mercury, and prevents fouling, oxidizing a d flouring conditions of the mercury.

Amalgamation takes placeat they point of contact of the mercury with the pulp which contains the-goldin liquid suspension, which-point of contact is termed the interface. Ihe water or pulp has a surface tension at this point, as has also the mercury. Thegold particles must be passed through these surface tensions at the interface and into the mercury itself in order to effect amalgamation. The passage of the current across the-surface of the mercury, with its attendant release of nascent hydrogenpcreates a spongy surface. on the mercury, as mentioned above, with lessened -surface tension and thus increased amalgamation.

surface tension and also increases the rate of `amalgamation. In the particular devices disclosed herein, -ithasl'neen found that interfalce pulsatlon can be favorably increased throughthe use of apulsating direct current.

creasing the effectiveness of the well known extraction processes, in such form as to be capable',

of addition to existing equipment without necsii tating costly alterations/or replacements. Other features and advantages of this invention will be apparent from the following description and the drawings,Y in which-f- .Fig. 1' is a perspective view of the amalgamating trough embodying this invention; Fis. 2 is .a

It has also been found that vl- Y bration of the mercury pulp interface, with its lattendant wave motions, reduces vthe effective sectional view along the lines 2 2 of Fig. 1; Fig. 3 is a vertical sectional view of centrifugal apparatus embodying this invention; Fig. 4 is a detailed fragmentary sectional view of the wall of the bowl; Fig. 5 is a schematic view of the wiring; Fig. 6 is a plan view of a trough illustrating a different embodiment of this invention; Fig. 7 is a bottom plan view of one of the transverse members in. Fig. 6; and Fig. 8 is a fragmentary sectional view along the line 8 of Fig. 6,

Referring more particularly 'to Figs. 1 and 2, an amalgamating trough Ill is shown formed of metal or other solid material. 'I'his trough is lined with an insulating material II, such as hard or soft rubber. Onthe inner 'surface of the rubber rests an amalgamating plate I2, which plate is preferably of silver or -of a silver-plated metal. On this amalgamating plate is a coating of mercury I3, which mercury substantially covers the entire bottom of the trough. In the walls of rubber, above the surface of the mercury but at a level adapted to contact a gold bearing pulp owing through the trough, are placed metal contact strips or electrodes I4 and I5. These elec trodes are relatively narrow strips, spaced a distance approximately equal to their length, and

connected by the lead wires I6 and I1 to the supply wires I8 and I 9. A suitable inlet orl supply means 20 is provided, and an outlet trough 2| serves as an exit for the pulp. .The trough may also, if desired, be provided with rimes 22.

In operation, the trough is supplied through the inlet means 20 with a continuous flow of pulp', comprising a multifarious liquid suspension.

This pulp spreads out, covers the entire lower surface of the trough to a depth substantially equal to the upper edges of the rows of electrodes I4 and I5, and passes through the trough and out the exit means 2I. The force of gravity tends to lcause the gold particles to drop to the bottom of the pulp, into contactwith the mercury-pulp interface. 'Ihe supply wires I8 and I9 are'fed with direct current, or with pulsating direct current, from any common source not here shown Ysince such source forms no part of the present invention. The flow of current transversely of the trough through the pulp, the interface, and the mercury considerably increases the speed of amalgamation, prevents the mercury from flourng, cleanses the mercury by a release of nascent hydrogen, avoids polarization and does not cause oxidizing or other undesirable effects in the merl cury.

Upon the completion of arrun, after substantially all of` the mercury has been amalgamated with gold, the amalgamating plate I2 is removed and the mercury gold amalgam thereon is treated for the recovery4 of the gold in any of the well known manners, as by ltration through chamois;

lsulting metallic residue.

followed by distillation of the thus separated concentrated amalgam, and acid treatment of the re- 'Ihe trough and plate may be then cleaned, the substantially pure mercury returned, and the trough is again ready for another run.

As disclosed above, the currentsupplied `to the electrodes through the wires I8 and I9 is preferably a pulsating direct current. Such a current may be supplied by a mercury arc rectier of the common commercial type, for example, or by superimposing an alternating current upon adirect current of a voltage at least equal to the peak voltage of the alternating current. As a theoretical explanation of the increased efilciency of the pulsating direct current as compared to the use of a pure direct current, it is believed that the periodic variations in surface tension at the mercury-pulp interface resulting from the changes in voltage tend to produce a surging to and fro of the interface, whereby amalgamation is promoted. These variations insurface tension are also believed to be effective in setting up wave motions and wave patterns in the interface, whereby the entrance of a gold particle into the mercury is pro'- moted, as long as such wave motions are not of such force as to produce cavitat'ion. It is to be understood, however, that whatever other explanation or theory might be developed to explain the action, it has been found that the arrangement herein described is actually of practical value in accelerating the amalgamation process, and that the invention is not concerned with the theory of operation just presented.

Referring more particularly to Figs. 3, 4, and 5, theinvention is4 shown embodied in amalgamating apparatus of the centrifugal type.`

' In the particular embodiment of the invention illustrated in-these figures the reference numeral 23 indicates a metal bowl or shell, which bowl is fastened to a rotatable member 24, as by the bolts 25. The rotatable member 241s supported by a shaft 26 riding on the thrust bearings 21, which bearings are journaled in a member 28 suppor-ted by the transverse member 29, which member is in turn supported by the frame 30. The shaft 26 may be provided with a ily wheel 3l 'to eliminate variations in the speed of rotation,

a second transverse member 35, which member is also supported by the frame 30.

The bowl 23 is here shown as having therein an inner bowl 36 of hard rubber, and an inner layer 31 of soft rubber, which layer is here shown as passing over the top of the hard rubber 36 and bowl 23 to form a flange 38. The soft rubber lining Aor bowl portion 21 has therein a continuous spiral groove 39. 'I'his groove is here disclosed in the preferred spiral form, although a series of concentric spaced annular grooves may be used. In the bottom of the groove the amalgamating plate or stripl 40 is fastened by any convenient means, as for example by Small cleats clinching into the soft rubber 31. Adjacent the edges of the grooves'are mounted electrodes 4I and 42. These electrodes do not contact the amalgamating strip 40, nor is there any direct electrical connection between them.

An inlet pipe or supply means 43 extends into the bowl substantially axially thereof, and is nonrotatably supported by the transverse member 44 mounted on the Iframe 30. An open spider or set of supporting arms 45 are rotatably journaled on the inlet pipe 43, as by the bearings 46, and contact the upper edge of the bowl, or of the lining 31, as at the point 41. This spider serves to steady the bowl, and to prevent vibration at high speeds of rotation. A dome or cupola member 48 covers the bowl, and an .outlet is provided for pulp flowing over the edge of the bowl by the sloping bottom`49 of the container 50, which container has an outlet opening 5I therethrough. The outlet may, if desired, be provided with a series ofrlles 52 to trap any mercury which may have escaped over the top of the bowl. The strips or electrodes and 42 are connected, respectively, to supply wires 53 and 54, as will be more 75 readily apparent from a consideration of Fig. 5. It will be noted that each row o f electrodes 42 are serially connected, the rows being connected in parallel to the supply wire'54. Similarly each series of electrodes 4| is connected to the supply wire- 53. The wires 53 and 54, referring back to Fig. 3, terminate in tips or jacks 55 and 56, mounted in the hard rubber extension piece 51,

, and adapted to be received by the sockets 58 the opening and 59, which sockets are mounted in the rotatable member 54. The lead wires 60 and 6I extend to the brushes S2 and 63, which brushes are adapted to contact the slip rings 64 and 65, non-rotatably mounted on a portion 66 of the transverse member 35. The rings 64 and 65 have connected thereto supply wires 61 and 68, through which current of any desired type mayA be supplied to the apparatus by means not shown here.

Referring more particularly to the fragmentary sectional view of Fig. ll, it will be noted that the grooves 3@ overhang, that is, they are wider at the bottom than at the top. This serves to enable f broader amalgamated surface, and to help prethe mercury from climbing over the edge the groove. trodes, as 4l and di?, are mounted in. the soft rubber immediately adjacent the edge of the groove, so that current flowing therebetween will be across the groove and partly through the mercury pulp interface. 'Ihe lead wires 53 and 5d are preferably mounted in grooves, as 69, in the hard rubber 36. It is to be understood that the upper supporting member 44 andthe inlet pipe 43 may be slid upward on the frame 30, or completely removed therefrom, whereupon the hard rubber bowl 3S and the soft rubberlining 3l may be lifted out of the metal bowl 23, the electrical connections separating where the jacks contact the sockets. A new lining piece may then ybe dropped .into the bowl, and the process of amalgamation continued while the mercury amalgam is being removed from the surface of the amalgamating plate 4U.

When the apparatus is in the condition illustrated in Fig. 3, a quantity of mercury suiiicient to cover the bottom of the grooves 39 and the amalgamating plate 40 therein is first poured into the supply pipe 43, andthe bowl is rotated to force the mercury up into the grooves. As soon as the mercury has substantially filled the entire groove, and has reached the uppermost level of the spiral, the ow of pulp is started into the bowl, A.the centrifugal force causes the pulp supplied to the lower central portion of the bowl to flow up the sides and over the flange 38, whereupon it flows along the bottom 49 and out During its passage up the wall of the bowl, however, the pulp has come intocontact with the mercury and has been .acted upon by the electric current, either pulsating or direct, and the combination of these factors with the centrifugal separation has caused substantially all of the gold particles in liquid suspension in the pulp to be amalgamated with the mercury. The direction of rotation of the bowl is preferably opposed to the direction of the spiral. groove, so that the tendency of thecentrifugal force to throw the mercury out of the top of the bowl 'is substantially neutralized. In order to keep the it will be noted that the elec-r is such for the speed of rotation used, for example 300 R. P. M., that gravity, the overhanging edges of the grooves, and the reverse trend of the spiral keep the mercury in the amalgamating grooves and do not throw it out oi the top of the bowl. The fact that the amalgamating plate is a continuous spiral, and that the electrodes are all interconnected serially by copper wires, also aids in maintaining uniform potential at every point of the amalgamating surface.

The effective action at the interface, and more particularly the cleansing action of the nascent hydrogen, is apparently increased in proportion to the extent ,that polarization is prevented. This is vpractically eliminated by such disposition of the terminals that they overlap eccentrically and are separated by insulation, but pass the pulsating direct current through the pulp to the interface of the mercury. This alternative arrangement of the terminals requires that they be carried by an additional member in close enough proximity to the amalgamating plate carrying the mercury to penetrate thel pulp stream and pass the current to the interface.

In a particular embodiment of this invention illustrated in Figs. 6, 7, and 8, the method of passing the current to the interface frdm'spirallyi arranged electrodes is illustrated\although any method of disposing the terminals of the electrodes to pass the current through the mercurypulpJ interface has been found to accelerate the amalgamating action. With ores where suliides are. troublesome, this form of application is found to be most effective. The/ reference numeral 15 indicates an amalgamating trough similar to that disclosed and described in connection with Figs. l

and 2. This trough has an inlet'l and an outlet 1l, and is adapted to have pulp, or an aqueous suspension of fine gold particles pass therethrough. The trough 15 has located therein and slightly raised above the level of the amalgamation plate 78, ledges or shoulders 19. These shoulders support transverse members 80, which transverse members are preferably formed of some insulating material resistive to the abrasive effect of the pulp. These transverse members 8U are spaced, and so arranged that a portion of the pulp flow passes beneath them and a portion above them, thus serving to create counter-currents and cross-flow which insure all of the pulp passing beneath the amalgamation plate 18 and the lower surface of at least one of the transverse members 80.

The under-surface of the transverse members .80 is com-posed of two different levels, one of these levels having mounted therein the spiral electrode 8|, and the other level having partially mounted therein the spiral electrode 82. The portion of the electrode 82 which is not mounted in the transverse member 80 itself, is supported therefrom by the small insulating blocks 83. These blocks insure good mechanical support of the electrode 82, without preventing the desired electrical action on `the pulp passing between the transverse memberill -andy the amalgamation plate 18. In this particular embodiment of the invention the electrode closest to the amalgamation plate, here disclosed as the electrode B2, is preferably the negative electrode for the application of the pulsating direct current. The negative electrodes in each of the transverse members are preferably connected in parallel to some supply line and current source, not here disclosed, and the positive electrodes are similarly connected.

Cil

'Ihe nascent hydrogen released by the passage ofcurrent .throughl the pulp seems to spread in a desirable manner from the electrodes of this type, and to effectively cleanse the mercury interface through its action. Since the electrodes overlap, cross-currents of nascent hydrogen are -apparently sent up, and little or no polarization of the mercury pulp interface occurs.

While we have shown and described certain embodiments of our invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction andarrangernent may be made without departing from the spirit and scope of the invention as disclosed in the appended claims, in which it is our intention to claim all novelty inherent in our invention as broadly as possible in view of the prior art.

What We claim as new, and desire to secure by Letters Patent, is: i

` 1. An amalgamation device of the character described, including: a container; an amalgamation plate in said container; a layer of mercury on said plate; a pair of electrodes in the walls of said container above the level of, and not in contact with the mercury, the sum of the distances from each electrode to the mercury being less than the interelectrode distance; means for passing a pulp comprising a liquld'suspension of particles of noble metal over said mercury; and means for passing current through the mercurypulp interface, said circuit passing current from one of said pair of electrodes to the other thereof.

2. A device of the character described for recovering particles of noble 'metal from a pulp comprising a liquid suspension of nely divided ore, including: a container adapted to be rotated. said container having a groove in the wall thereof; an amalgamation plate in said groove; means for maintaining a layer of mercury on said plate in said groove; apair of electrodes in the Walls of said container on opposite sides of said groove, said electrodes being above the level of said mercury; means for passing said pulp over said mercury; and means for passing an-electric current through the mercury pulp interface, said means including said electrodes.

v3. A device of theA character described for recovering particles of noble metal from a pulp comprising a liquid suspension of finely divided ore, including: a container of substantially parabolic cross-.sectional shape, said container being adapted to be rotated; a groove in the wall of said container; an amalgamation plate in the bottom of said groove; means for maintaining a layer of mercury on said plate, said means including rotation of said container; a pair of electrodes in the Walls of said container adjacent opposite edges of said groove, said electrodesbeing above the level maintained by said mercury; means for passing said pulp over said mercury; and means for passing an electric current through the mercury pulp interface, said means including said electrodes.

4. Apparatus of the character claimed in claim 3, wherein said current is a pulsating direct current.

5. A device of the character described for recovering ,particles of noble metal from a pulp comprising a liquid suspensionof nely divided ore, including: a container of substantially parabolic cross-sectional shape having a spiral groove in the wall thereof, said container being adapted to be rotated in a direction opposed to said spiral;

u an amalgamation plate in the bottom oi' said groove; means for maintaining a layer of mercury on said plate; electrodes in the walls of said container between the edges of adjacent turns of said spiral, said electrodes being adjacent the edges of said groove and above the level of the mercury therein; means for passing said pulp continuously over said mercury; and means for passing an electric current through the mercurypulp interface, said means including the electrodes.

6. Apparatus of the character claimed in claim 5, wherein said current is a pulsating direct current.

'7. A device of the character described for recovering particles of noble metal from a pulp comprising a liquid suspension of finely divided ore, including: a container of substantially parabolic cross-sectional shape, said container'having a. spiral groove in the wall thereof; means for rotating said container in a direction opposed io said spiral; an amalgamation plate in said groove; means for maintaining a layer of mercury on said plate; means for continuously passing pulp over said mercury, said means including an inlet substantially axially disposed in said container; electrodes in the walls of said container between the edges of adjacent turns of said groove, said electrodes being above the level of said mercury; and means for passing an electric current through the mercurypulp interface, said means including said electrodes.

8. Themethod of extracting a metal from an ore pulp by vamalgamation with mercury, in which the pulp is brought into contact with the mercury and simultaneously an electric current is passed through the pulp, the mercury and the mercury-pulp interface from a pair of electrodes above the level of, and not in contact with said mercury, the sum of distances from each electrode to the mercury being less than the inter-electrode distance.

9. The method of extracting a metal from a pulp comprising an aqueous suspension of particles of the metal in which the pulp is brought into contact with mercury and simultaneously an electric current is passed from an electrode into said pulp across said mercury-pulp interface, and out of said pulp through another electrode, neither of said electrodes being in contact with the said mercury and the sum of the distances from each electrode to the mercury being less than the inter-electrode distance.

10. The method of extracting a metal from a pulp comprising an aqueous suspension of fine particles thereof in which the pulp is brought into contact with mercury and simultaneously a pulsating direct current is caused to flow across he mercury-pulp interface from a pair of electrodes above the level of, and not in contact with, said mercury, the sum of the distances from each electrode to the mercury being less than the interelectrode distance.

l1. rlhe methodof extracting a metal from a pulp comprising and aqueous suspension of the metal, in which the pulp is brought into contact with mercury and simultaneously an electric current is passed through a pair of electrodes above the level of, and not in contact with, the said mercury, the sum of the distances from each electrode to the mercury being less than the interelectrode distance, said pulp, mercury-pulp interface, and mercury in a direction substantially parallel to the plane of said mercury-pulp interface.

12. A device of the character described for reoppositeed'ges of hsaid groove, said electrodes blel i for passing an. electric current through the mercoveringl particles'of noble metal from a pulp -Ycompyrising a liquid ,suspension of nely divided ore, includingzal containerof substantially parabolic-cross-sectional shape, said`container being adapted to brrotated; /a spiral groove in the wall' of said container; an amalgamation plate in the' cluding rotation of said container; aV pair lof electrodes in the walls of said container adjacent ing above the level maintained by said mercury; means for 'passing' said pulp over said mercury;

-and means for passing an electric current through n the mercury pulpv interface, said means including'said lectrodes.

`13. A device of the character described for re# covering particles of noble ,metal from a pulp comprising a. liquid suspension f iinely divided ore, including: a container of substantially para- `mercury on 'said plate; means foi` passing said pulp continuouslyvoversaid mercury; and -means cury pulp interface, said means including electrodes.

'CHARLES REVELL. HLDEN. MIGUEL DRoBrNsKY. 

